Throughout the years I created a few circuits, used by me for research and development or just for fun. By checking the internet on projects, due to the size of the internet, limited can be gathered. Thats the main reason for this page, to give guys like me information on things I already created. Oh, and :
I CAN NOT BE HELD RESPONSIBLE FOR ANY DAMAGE MADE BY BUILDING THESE CIRCUITS!!!!
Am I the only living sole on earth really needing to have a NiMH battery charger with a current of 50 to 500mA? I thought so after a few months of chopping and not finding a unit like that! Yes, well, you can buy units like that but they where to expencive! And so I started to create one myself. Below the schematic (click for enlargement).
The circuit excists of two parts, the charger and the decharger wich can be switched off. When batteries are connected and they are not really empty, the circuit starts decharging them (yellow LED) till the minimum voltage is reached (1V1 per cell). The charging circuit will automatically start charging the batteries ( green LED) till the maximum voltage is reached (1V4 per cell). When the red LED is on, the batteries are charged and if not the circuit is measuring the voltage of the cells.
The three switches in the circuit have the possibility to charge 2 or 4 cells. They all switch together ( One switch with more contacts).
With the ">220R" potentiometer, the charge current can be adjusted. Check the batteries to be charged for the right current!
The circuit was build, as all prototypes build by me, on euroboard and a enlargement can be viewed by clicking on the image below.
Black spots indicate where something external, like a LED, is to be connected and the info about it is put in the same line on the side of the board
1 CEL NIMH CHARGER
After a while I really needed a charger that could charge cellls independantly. Thought the BQ2002 could do the trick and after a period of playing with resistor values and tests, the whole thing came together. Below the schematic.
The charge current has been fixed at 450mA. Having four of these circuits in a casing for four batteries, you'll need a 5V, 2,5 A external power supply.